Liquid, neutralization and scrubbing media is normally used for removal of acidic media (like oxides of Sulphur) present in fossil fuel fired flue gas. Highly Alkaline substance like Caustic Soda, Milk of lime etc are usually mixed in water and the dissolved solution is used as a liquid neutralization and scrubbing media in a direct contact scrubber. It is also normally not economical to neutralize the acidic media present in the flue gas by this method leading to the flue gas being dissipated into the atmosphere without scrubbing and cleaning.
Scrubbing the hot and dirty fossil fuel fired gas with seawater in a direct contact venturi scrubber/packed column is also carried out to trap the suspended particulate matters present in the flue gas as well as to neutralize the acidic media present in the flue gas with the alkaline matter present in seawater/scrubbing liquid. The pressure drop across the venturi scrubber increases the turbulence between the scrubbing liquid and the hot and dirty flue gas leading to intimate contact between them. This ensures neutralization of acidic media present in the flue gas as well as trapping of suspended particulate matter present in the flue gas—in the scrubbing liquid.
Waste heat present in fossil fuel fired flue gas which is normally being dissipated into the atmosphere can be used to evaporate some water from seawater. The concentrated seawater can then be used to neutralize the acidic gaseous media present in the same flue gas as long as the seawater is recycled with a bleed and not passed through the scrubber as once through.